[Report of initial experiences in establishing a regional multicenter evaluation of lymphocyte typing with flow...

Participation in a multicenter evaluation of flowcytometric investigations is the only possibility of providing external quality control. Up to now nine different laboratories have taken part in this program, measuring two samples of fresh EDTA blood according to a recommended antibody panel. The choice of antibodies was intended to reach a standardized immune status. Three different types of flowcytometers were used. All results were expressed in lymphocyte subset percentages and in absolute values. The coefficient of variation of each lymphocyte subpopulation was used for interpretation of the results of all working groups, as well as the control measurement. The results of the control measurement already showed that there was a difference between the obtainable coefficient of variation for the different subpopulations. In the case of CD3, CD4 and CD8 positive lymphocytes the relative percentages of the total group gave values far below 10%. The coefficients of variation of the activated T-lymphocytes or the cytotoxic T-cells, as well as of the absolute values were definitely higher. Already after the second multicenter evaluation the achieved results showed positive aspects such as improvements of the outcome, advancement of the user contacts, cooperation and impulses by discussing interesting problems.